The present disclosure relates to a sheet feed device including a cassette which is fittable and removable to an apparatus body and which contains therein sheets to be fed to the apparatus body. The disclosure also relates to an image forming apparatus including the sheet feed device.
In image forming apparatuses such as copiers and printers, use is made of a sheet feed cassette in which a sheet bundle of cut paper or the like is preparatorily stocked and which separates and feeds sheets one by one from the sheet bundle, starting with the topmost layer of the bundle. For such purposes as resupply of sheets and changes in sheet size, or on occasions of jam treatment, the sheet feed cassette is fitted to and removed from the main body of the image forming apparatus by a user's manual work.
Also, with an aim of preventing the sheet feed cassette from popping out during image formation, the sheet feed cassette is biased, in an insertional direction, against the image forming apparatus body. Due to this, a user would be necessitated to pull out the sheet feed cassette with a force greater than the biasing force acting on the sheet feed cassette. Furthermore, on occasions involving a large total weight of the sheet feed cassette's own weight and contained sheets' weight, operability in pulling-out the sheet feed cassette from the main body of the image forming apparatus would be deteriorated.
Accordingly, there have been proposed methods that allow the sheet feed cassette to be easily pulled out with simple structure. As an example, there is known a sheet feed cassette with a sheet pushup-pressure canceling function which includes: a push-up member whose one end is pivotably attached on a bottom plate of a sheet feed cassette body and whose other end pushes up an other-end lower surface of a sheet mounting plate; a biasing means for upwardly biasing the other end of the push-up member; a pushup-pressure canceling means which operates in linkage with the pushup member to cancel a sheet pushup pressure applied to the sheet mounting plate by the biasing means; and a pushup-pressure cancellation actuating member for actuating the pushup-pressure canceling means in a sheet-feed-cassette pull-out position.